The difference you’re looking at is wraps vs. splints.
The KH and 661 simply wrap around your wrist with a stiff material to prevent hyperflexion… your hand still experiences some of the forces of impact.
The Harbinger gloves include a splint that holds the wrist in place, absorbing most of the forces of the impact. The KH glove, instead, places extra padding on the palm. I find this to be adequate for most situations… riding on the street or offroad.
For the protection you gain with the Harbinger, you give up flexibility and grip. Personally, I find it difficult to get a good grip on the KH handle with Harbingers… which is why I don’t use such gloves.
Of course, if you’ve any pre-existing hand, wrist or forearm injury, you’ll want the extra protection of the Harbingers.
One last thing… fingertip protection. “Cutoff” gloves leave your fingers exposed to whatever they may impact. I’ve seen riders picking gravel out of their fingers before… not cool. Get full fingered gloves!
My 2 cents.
Have you ever heard of a "RSU is not a chat room.